1. Field of the Invention
This invention relates to an ink jet printer which is capable of removing thickened ink by cleaning, flushing, or the like.
2. Prior Art
Conventionally, this kind of ink jet printer removes ink (hereinafter referred to as "thickened ink") which is solidifying through evaporation of a solvent, such as water in the case of a water-soluble ink, by cleaning or flushing.
For example, the thickened ink is removed when printing is started after the lapse of a predetermined time period from termination of the immediately preceding printing operation, or when printing is started after replacement of an ink cartridge, or when the user has found a defective print quality, or on like occasions. In removing the thickened ink, as shown in FIG. 1, a head cap 24 is brought into intimate contact with a print head 21 which is arranged at an end of a carriage 23 having an ink cartridge 29 loaded therein, whereby nozzles 22 of the print head 21 are blocked. Then, a pump 28 is operated to collect or draw the thickened ink via an ink absorbent 25 and an ink collecting tube 27 into an ink absorbent 26. Alternatively, wiping or wrapping of the surface of the print head 21, that is, cleaning of the same, is carried out.
When the printer has continued to be in an operating state in which the head cap 24 is not in intimate contact with the print head 21 over a predetermined time period, or when printing is terminated, the carriage 23 is returned from a printing area PA to the home position HP to bring the print head 21 into contact with the head cap 24, and then a slight amount of ink is caused to be delivered through all the nozzles 22 of the print head 21. In short, flushing is carried out. Further, immediately after the main power supply is turned on, one of or both of the cleaning and flushing operations are carried out. Through these operations, thickened ink formed at openings of the nozzles 22 and ink passages adjacent thereto is removed to thereby prevent the nozzles 22 and the passages from being clogged.
However, according to the conventional ink jet printer, even if the printer is in a non-printing state, i.e. in a state where the print head 21 is in intimate contact with the head cap 24, if the printer is left unused with the ink cartridge 29 loaded therein for a long time period (e.g. several months), portions of ink not only within the nozzles 22 but also within ink passages extending from the ink cartridge 29 to the nozzles 22 solidify through evaporation of a solvent or water, so that the nozzles 22 and the ink passages are clogged. In such cases, the cleaning and/or flushing normally executed when the printer is started is not sufficient for restoring a normal operative state of the printer in which printing can be properly carried out. To recover from such a malfunction of the printer, it is required to set a new ink cartridge 29 to dissolve the solidified ink, or to carry out the cleaning of the print head 21 several times by the use of the pump 28, further, if required, to replace the print head 21 by a new one, which prevents the user from using the printer immediately as he desires, and causes him to take the trouble of restoring the normal operative state of the printer.